Prepreg is a composite consisting of fiber reinforcements preimpregnated with resin, which is typically molded with pressure or vacuum to provide a variety of molded articles. Prepregs have applications in aerospace, transportation, appliances, sanitary ware, and the like.
Various techniques for making prepreg are well known. For example, U.S. Pat. No. 4,495,017 to Abe et al. proposes a process for continuous production of prepreg sheets. The process involves contacting fiber bundles with a solvent and continuously taking up the individual fiber bundle units under tension over curved surfaces of spreader bodies, thereby spreading out and drying the fiber bundles. According to this method, the fiber bundles are spread with a solvent prior to being impregnated with a resin. U.S. Pat. No. 3,959,209 to Lake proposes a curable solid polyester resin prepared by mixing a polyester and crosslinking agent with one or more of a filler, fibrous reinforcements or amorphous polyester. U.S. Pat. No. 4,892,764 to Drain et al. also proposes fiber/resin matrices and a method for making them. Drain et al. proposes a method of making a filament wound article including rotating a mandrel, impregnating a winding filament with a resin composition comprising an actinic radiation-cured first resin component and a curable second resin component, filament winding the mandrel, exposing the wound filament to actinic radiation contemporaneously with filament winding, terminating the rotation of the mandrel, and curing the second resin component.
Although several means of producing formable prepreg have been proposed, there remains a need in the art for a method of preparing continuous prepreg which is faster than conventional methods and can be automated. Conventional forms of prepreg include sheet molding compound (SMC), which typically requires extensive manual labor in preparation and final molding. Additionally, SMC produces waste in the form of carrier film, and trim waste produced by cutting the SMC into desired shapes. Accordingly, there is also a need in the art for a method of making prepreg which reduces the amount of waste produced by conventional techniques.
In addition, there is a need in the art for a method of preparing prepreg which achieves a more efficient use of fiber reinforcements. Conventional SMC technology is limited with respect to the ability to optimize the placement of reinforcing fiber in the SMC. Accordingly there is a need in the art for a method of making prepreg which improves on efficient use of fiber reinforcements. In addition, the method of the present invention allows more reinforcements to be added to the prepreg composition than conventional methods.
There is also a need in the art for a method of preparing prepreg which permits the optimization of conditions of the method of preparing prepreg to provide a more efficient and designed product. Conventional methods of preparing prepreg permit only limited control over the conditions under which the prepreg is prepared, thus restricting the ability of the artisan to optimize the product by controlling a variety of reaction conditions. The method of the present invention, permits more thorough impregnation of the reinforcing fibers by providing the ability to apply pressure and dearation during the impregnation process. In addition, environmental conditions, such as temperature and atmosphere, can be controlled in the method of the present invention.